2.5 3.0 not worried

When the libre shows really low levels like that you need to do an actual blood test to see what its actually at as the libre can be very inaccurate below 5. Mine has shown 2.8 before when it was actually at 5.3.

Our surgery gives out the Nexus RX to type 2's but says it's not accurate enough for type 1's so they gave me a Nexus RX HCT. I found the RX to be out at the lower and higher range of BS's by more than 1-2 mmol/l (compared to my routine blood test taken at the same time.)

Your readings still could be plus 15% according to their site, which I found only in the BS normal range.
https://www.glucorx.co.uk/diabetes/...Nexus meters comply,YSI-2300 glucose analyser'.

You would need further testing to see what was going on.

Yes, it could be your cgm, but because you only had a two hour oral glucose tolerance test, how can your doctors say that nothing is going on?
You need an extended OGTT, this will tell you if your blood glucose levels drop after two hours, like I do!
Keep testing and recording your results. In my experience Hypoglycaemia is something that needs to be sorted if you are experiencing hypoglycaemic episodes.

Because you have to convince your doctors you need further tests, having a cgm, food diary and symptoms, it could be something else but unless and it's highly unlikely, you could be, like me, misdiagnosed, that it is negligent to dismiss symptoms like you describe because those symptoms are prevalent in many metabolic conditions and pancreatic conditions as well as hypoglycaemic conditions.

You can do a test at home with a high carb meal and monitor your blood glucose levels fasting before, one, two, three and if necessary four hours after.
This is not an actual supervised test as is done in hospital, because the hospital test is 75g glucose. It will give you an idea of what your response to carbs are. And if you actually go hypo. Use your cgm, and verify with your other monitor.